Mineral wool composition

ABSTRACT

The invention relates to &#34;two-component&#34; inorganic fibers obtained by conjoint fiber formation from two different inorganic compositions, especially two glass compositions based on SiO 2 , alkali metal oxides and alkaline-earth metal oxides; 
     the two inorganic compositions have thermal expansion coefficients α exhibiting a difference Δα of at least 20×10 7  K -1 , 
     they have a minimum viscosity temperature of fiber formation T log3  of between 830 and 1010° C., 
     they exhibit a work range of at least 30° C., 
     each includes, as weight percentages, in all less than 3% of the following compounds: TiO 2 , ZnO, BaO and Li 2  O and preferably less than 1% of each of these, 
     they exhibit, as weight percentages, differences in respective contents of boron oxides B 2  O 3  and of sodium oxide Na 2  O such that: 
     
         (i) ΔB.sub.2 O.sub.3 &gt;2% 
    
     
         (ii) ΔNa.sub.2 O&gt;2%.

This application claims the benefit of U.S. Provisional Application No.60/054,539 Aug. 4, 1997.

The present invention relates to the field of artificial mineral wools.It concerns more precisely the mineral wools intended for themanufacture of materials for thermal and/or sound insulation orsubstrates for soilless cultivation, and especially those commonlyreferred to by the term of glass wool.

Mineral wools of glass wool type with which the invention is concernedare generally obtained by so-called internal centrifuging processes offibre formation, consisting, in outline, in pouring the vitrifiable rawmaterials, once they are molten, inside centrifuges (spinner) whoseperipheral wall is pierced with a large number of orifices from whichthe molten mass is thrown forward in the form of filaments which areentrained and drawn into fibres by a gas stream at high temperature andspeed at the periphery of the centrifuges.

An adaptation of the internal centrifuging technique described above hasbeen developed, an adaptation consisting, again in very rough outline,in feeding each of the orifices of the fibre-forming spinner with twoglass threads exhibiting different chemical compositions. Since theglass compositions are chosen so as to have different heat expansioncoefficients α, the fibres obtained are found to be "two-component"fibres which, on cooling, exhibit a high flexibility and a "curvilinear"appearance giving the final product a particularly aerated, particularly"blown" or <<puffed>> appearance with a high recovery of thickness aftercompression. Reference may be made, for example, to patents U.S. Pat.No. 2,998,620, WO-95/12554 and WO-96/34837.

Investigations have also been conducted in order to develop the mostjudicious "pairs" of glass compositions, to obtain the property soughtafter.

Thus, the abovementioned patent application WO-95/12554 describescombinations of two types of glass compositions in which the differencebetween the thermal expansion coefficients is at least 20×10⁻⁷ K⁻¹.However, the two types of compositions adopted have a temperaturecorresponding to a viscosity in poises equal to log 3 which is between1010° C. and 1121° C. In concrete terms, this temperature, calledT_(log3), is for a person skilled in the art an indication of thetemperature of minimum viscosity for fibre formation. Now, the abovetemperature range 1010-1121° C. is particularly high, and this is notfree from disadvantage in terms of fibre formation: in particular itinvolves high energy expenditure for melting the raw materials and arisk of premature corrosion of the fibre-forming spinners.

The abovementioned patent application WO-96/34837, in its turn, haschosen especially to add oxides of Li₂ O, ZnO, BaO or TiO₂ type to thecompositions in order to modify their thermal expansion coefficients aswell as possible, or else to employ particularly high boron oxide ratiosfor the compositions with the lowest thermal expansion coefficient.However, in both cases, these choices result in an appreciable increasein the costs of raw materials.

The aim of the invention is to overcome these disadvantages, especiallyby developing new combinations of inorganic compositions which arecapable, once conjointly formed into fibres, of exhibiting the wavyappearance sought after, by virtue of a sufficient difference betweentheir respective thermal expansion coefficients. However, the inventionalso seeks to make the production of such fibres feasible, industriallyand economically, and especially not expensive in terms of yield, ofcosts of production tools, of energy costs or of raw materials.

The subject-matter of the invention is therefore "two-component"inorganic fibres obtained by conjoint fibre formation from two differentinorganic compositions, especially two glass compositions based on SiO₂,alkali metal oxides and alkaline-earth metal oxides. They are defined bythe following characteristics:

a)--the two inorganic compositions have thermal expansion coefficients αexhibiting a difference Δαof at least 20×10⁻⁷ K⁻¹ between thecomposition "of highest α" and the composition "of lowest α", andespecially of at least 30×10⁻⁷ and even 40×10⁻⁷ K⁻¹,

b)--the two inorganic compositions have a minimum viscosity temperatureT_(log3) of between 830 and 1010° C.,

c)--the two inorganic compositions exhibit a work range defined by thedifference between the temperature of minimum viscosity for fibreformation and the liquidus temperature, of at least 30° C., especiallyof at least 40° C.,

d)--each of the two inorganic compositions includes, as weightpercentages, in all less than 3% of the following compounds: TiO₂, ZnO,BaO and Li₂ O, and preferably less than 1% of each of these,

e)--the two compositions exhibit, as weight percentages, differences inrespective contents of boron oxides B₂ O₃ and of sodium oxide Na₂ O suchthat:

    ΔB.sub.2 O.sub.3 >2%                                 (i)

    ΔNa.sub.2 O>2%.                                      (ii)

According to the invention there is in addition preferably the followingrelationship:

    0≦|ΔNa.sub.2 O-ΔB.sub.2 O.sub.3 |≦5.                                      (iii)

In the context of the invention "ΔB₂ O₃ " in relationship (i) isintended to mean the difference between the B₂ O₃ content, as weightpercentage, of the composition "of lowest α" and the B₂ O₃ content, asweight percentage, of the composition "with highest α".

Similarly, ΔNa₂ O in the relationship (ii) is intended to mean thedifference between the Na₂ O content, as weight percentage, of thecomposition "of highest α" and the Na₂ O content, as weight percentage,of the composition "of lowest α".

In the relationship (iii), it is indeed the absolute value of thedifference ΔNa₂ O-ΔB₂ O₃ that is considered: here, the difference can,in fact, correspond to a positive or negative value. Furthermore, theT_(log3) temperature value corresponds to the temperature at which thecomposition(s) considered is (are) at a viscosity, expressed in poises,corresponding to log 3.

In the light of all the characteristics stated above, the invention hasin fact achieved a judicious compromise between the various propertiessought after for this quite special type of fibre.

Thus, the characteristic a) guarantees that wavy fibres, and hence themineral wool exhibiting the "swollen, puffy >> aspect which isparticularly advantageous from the thermal and mechanical viewpoint,will actually be obtained. In fact, a minimum difference of 20×10⁻⁷ K⁻¹between the two thermal expansion coefficients is necessary. A Δα of theorder of 30 or even 40 to 50×10⁻⁷ K⁻¹ is preferably rather chosen.

The characteristic b) specifies a range of T_(log) 3 temperature valueswhich are advantageous because they lie below 1010° C. and are ratherincluded between 850 and 1010° C., and especially of at least 860° C.,or even optionally of at least 890° C., that is to say temperatureswhich are relatively not very high, which is obviously very highlyadvantageous, both in terms of the cost of energy of fibre formation andof production tools. In fact, the centrifuging spinners are thus foundnot to be too highly stressed thermally and wear normally without havingto resort to expensive materials suited to the high temperatures. TheT_(log3) values of the two compositions are preferably near each other,advantageously with a difference of at most 30° C., especially of atmost 25° C., more particularly of at most 20° C., to guarantee anoptimum compatibility of their fibre-forming conditions.

The characteristic c) is a work range defined above, sufficiently broadto permit fibre formation in standard conditions, this range ispreferably at least 40° C., and even advantageously above 50° C.

The characteristic d) tends to limit the cost connected with the rawmaterials: in fact, the invention makes it possible to obtain fibreswith the property sought after, without having to resort to componentsin quantities such that their cost would overload the profitability ofthe manufacture.

The characteristic e) of the invention puts forward the relationships(i) land (ii) between the Na₂ O and B₂ O₃ contents of the twocompositions. The invention have shown, in fact, that sodium oxide andboron oxide has an influence on the thermal expansion coefficient α insimilar proportions but opposite directions, sodium oxide tending toincrease the coefficient α whereas boron oxide tends to decrease it.Rather than add very special oxides in order to influence thecoefficient α, oxides which have only this effect and which aregenerally very expensive, like Li₂ O or ZnO, the invention has thereforebeen based on compositions with customary constituents: sodium oxide andboron oxide are well-known components for adjusting the viscosity of thecomposition, being included among the fluxes and/or lattice-modifiers inthe inorganic composition. The invention therefore assigns to them asecond function, that of "regulators" of the coefficient α, so as toobtain the desired difference in coefficient α between the twocompositions.

What is astonishing, furthermore, is that this "second function" hastherefore led to the selection of the minimum differences between Na₂ Oand B₂ O₃ contents, defined by the relationships (i) and (ii), withoutthese adjustments to Na₂ O and B₂ O₃ contents coming to perturb theiroriginal function. It has thus been possible to maintain, in parallel,T_(log3) and liquidus temperature values which are wholly suited to thestandard conditions of fibre formation by internal centrifuging. Itmight have been expected that, on the contrary, such adjustments wouldhave unforeseen consequences on the "fibre-formability" of thecompositions. In fact, within the scope of the invention it is possibleto "allow oneself" to choose two compositions whose sodium oxide andboron oxide contents remain within proportions that are not necessarilyunusual, since the reasoning is based on differences.

It should be noted that the invention emphasizes chiefly Na₂ O as anagent capable of increasing the coefficient α, but that other alkalimetal oxides can play this part, very particularly K₂ O. In fact, it ispreferred in the invention to employ little or no K₂ O, generally atmost 10%, especially at most 8% or 5% or 3%, because this originatesfrom a raw material which tends to be slightly more expensive than Na₂O. If all the alkali metal oxides are expressed as R₂ O, it is thenpreferred in the invention to choose the ratio of the weight percentagesNa₂ O/R₂ O which is relatively high. Without departing from theinvention it is possible to consider in the relationship (ii) not Na₂ O,but, in fact the sum (Na₂ O+K₂ O).

It should also be noted that the optional relationship (iii) "expresses"the fact referred to above, that these two oxides have an influencewhich is opposite but in similar proportions. From the composition "ofhigh α" to the composition of "low α" the "deficiency" of "boron oxide"is thus found to be "compensated" at least partially, by an "excess" ofsodium oxide and vice versa.

It may be emphasized that, even in the composition "of low α ", which istherefore found to be that richer in B₂ O₃ of the two, according to theinvention it is preferred to limit the boron oxide content to at most20% by weight, since an excessive proportion of boron oxide could turnout to be disadvantageous in terms of cost of raw materials inparticular.

According to an embodiment of the invention at least one of theinorganic compositions includes, as weight percentage, at least 0.5 to1% of aluminium oxide. While this does not appear to have a significantinfluence on the expansion coefficient α, on the other hand providing itin a certain quantity tends to improve the durability of the fibres,especially with regard to water attack or to high temperature. It may bepreferable, nevertheless, to limit its content to at most 3.5% byweight.

According to another embodiment of the invention, compatible, of course,with the preceding one, at least one of the two compositions includes,as weight percentage, from 0 to 3% of P₂ O₅, especially either 0% of P₂O₅ or from 0.1 or alternatively from 0.5 to 2% of P₂ O₅. Thisconstituent may fulfil an advantageous function: it is known, in fact,that it tends to have a positive influence on the biodegradability ofthe fibres, which is tested by suspending in a buffered mediumsimulating a physiological medium, without very significantly alteringthe thermal expansion coefficient α. There is therefore an advantage inresorting to it in the compositions. A maximum proportion of 3 or 2% ispreferable, in order not to overload the raw material costs.

According to another embodiment, still compatible with the precedingones, at least one of the compositions may comprise at most 3% of K₂ Oand, preferably, between 0 and 2% of this oxide. In fact, K₂ O acts as aflux, like Na₂ O, and tends to increase the coefficient α, as explainedabove. It is nevertheless preferable to limit its content by keeping thesum of the alkali metal oxide contents of each of the two compositionsconstant, because potassium oxide tends to be more costly than sodiumoxide.

According to another alternative form, compatible with the precedingones, at least one of the compositions may contain from 0 to 3% byweight of Fe₂ O₃ (total iron expressed in this form) and/or may containup to 3% by weight of fluorine.

According to another alternative form, compatible with all those above,at least one of the compositions may contain less than 3% by weight ofBaO.

The invention defines below four major types of inorganic compositionsof glass type, labelled A, B, C and D and classified according to adecreasing thermal expansion coefficient α. The most advantageouscombinations between two compositions belonging to different types willbe made explicit in what follows. In each of these classes, and in allthe compositions exemplified in what follows, it is to be understoodthat these compositions may optionally contain elements/oxides otherthan those explicitly mentioned. This may especially involve optionalelements/compounds referred to above, of the P₂ O₅ and Fe₂ O₃ type. Aperson skilled in the art of the field of glass-manufacturingcompositions is aware, furthermore, that the latter may also comprise,without any limitation being implied, a certain content of impurities,generally at most 2% by weight.

The first class of compositions is so-called of type A. It has a thermalexpansion coefficient α of between 110 and 140×10⁻⁷ K⁻¹, and includessodium oxide, boron oxide and optionally K₂ O in the followingproportions, as weight percentage:

B₂ O₃ ≦7%, preferably lower than 5%, especially from 0 to 4% or 0 to 3%,

Na₂ O≧18%, preferably from 19 to 25%,

Na₂ O+B₂ O₃ +K₂ O between 18 and 33%, especially between 22 and 30%.

This sum (Na₂ O+B₂ O₃ +K₂ O) is an advantageous index of the overallcost of raw materials needed for the formulation. It can be considered,in fact, that in the compositions according to the invention, the chiefconstituents of which are the standard constituents of glasscompositions, it is sodium oxide and boron oxide which, by thequantities employed and their price, define a significant part of theoverall cost of the composition. Another important point is that thissum (Na₂ O+B₂ O₃ +K₂ O) plays a great part in determining the T_(log3)value of the composition.

The composition of type A preferably includes the following compounds,as weight percentages:

    ______________________________________    SiO.sub.2    46 to 62%,                           preferably 48 to 60%    Na.sub.2 O   18 to 26%,                           preferably 19 to 25%    B.sub.2 O.sub.3                 0 to 7%,  preferably 0 to 4%    Al.sub.2 O.sub.3                 0 to 8%,  preferably 0 to 5%    K.sub.2 O    0 to 8%,  preferably 1 to 4%    CaO          6 to 13%, preferably 7 to 12%    MgO          0 to 5%,  preferably 0 to 3%    P.sub.2 O.sub.5                 0 to 3%.    ______________________________________

This series is of interest in the sense that it is aimed at compositionsof high or even very high coefficient α since, in the case of some ofthe examples 1A-18A which illustrate this class in the text thatfollows, the coefficient α exceeds 130×10⁻⁷ K⁻¹.

All the compositions in this class have two points in common: a highproportion of alkali metal oxides and very particularly of sodium oxide,and a low, or even nil proportion of boron oxide.

It is next possible to distinguish several "subgroups" in this class,according to various criteria linked with their compositions.

Thus, some have a significant proportion of aluminium oxide, of theorder of 5 to 8%, whereas others have a much lower or even virtually nilproportion of aluminium oxide, of the order of 0.5 to 3%. Aluminiumoxide tends to increase the durability of the fibres, it being possiblenevertheless for too high a proportion not to be desirable because ofother considerations; the invention therefore allows a wide choice inthe proportion of alumina, while keeping the values of α and of T_(log3)within similar values, which can be ascertained especially from thecomparison of Examples 11A and 16A, or 14A and 16A, detailed below.

Compositions which have P₂ O₅, especially between 0.5 and 2%, can alsobe distinguished from those that do not have it. In fact, the presenceof P₂ O₅ can improve the biodegradability of the fibres, especially ifit relates to compositions in which the proportion of alumina issignificant.

It is also possible to distinguish the compositions which have boronoxide, especially in modest proportions of the order of 1 to 3%, fromthose which are devoid of it.

Where the adjustment of the coefficient α is concerned, it is, in fact,advantageous here to introduce little or no B₂ O₃, since it tends tolower this coefficient. Its presence in these compositions "of high α"can nevertheless be justified by its original function of a flux.

The second class of compositions is so-called of type B. It has athermal expansion coefficient α of between 100 and 109×10⁻⁷ K⁻¹, and itincludes sodium oxide and boron oxide, and optionally potassium oxide inthe following proportions, as weight percentage:

B₂ O₃ ≧3%, preferably≧4% and especially from 4 to 7%,

Na₂ O≦22%, preferably≦20%, especially between 16 and 20%,

Na₂ O+B₂ O₃ +K₂ O between 15 and 28%, especially between 18 and 25%.

The composition B preferably includes the following compounds, as weightpercentages:

    ______________________________________    SiO.sub.2    56 to 65%,                           preferably 58 to 62%    Na.sub.2 O   15 to 22%,                           preferably 16 to 20%    K.sub.2 O    0 to 3%,  preferably 1 to 2.5%    B.sub.2 O.sub.3                 3 to 10%, preferably 4 to 8%    Al.sub.2 O.sub.3                 0 to 3%,  preferably 1 to 2.5%    CaO          6 to 10%, preferably 7 to 9%    MgO          0 to 5%,  preferably 1 to 4.5%    P.sub.2 O.sub.5                 0 to 3%.    ______________________________________

It is seen that this time it is a minimum proportion of boron oxide thatis imposed and, on the contrary, a maximum proportion of sodium oxide.What is again involved is rather a composition "of high α" type(although it is not ruled out that it may be made to act as acomposition "of lower α", for example in combination with a compositionof type A), but it is aimed at a range of lower coefficients α.

This involves a class of compositions which are somewhat intermediatebetween the compositions of very high α referred to above and thecompositions of very low α described later under the heading of class oftype D. The proportion of Na₂ O tends to be slightly less high than inclass A and, on the other hand, the presence of B₂ O₃ is required. Thesum (Na₂ O+B₂ O₃ +K₂ O) also tends to be less high than in class A.

The third class of compositions is so-called of type C. It has a thermalexpansion coefficient α of between 76 and 99×10⁻⁷ K⁻¹ and it includessodium oxide, boron oxide, and optionally potassium oxide in thefollowing proportions, as weight percentage:

B₂ O₃ >10%, preferably>11% and especially between 11 and 16%,

Na₂ O≦18%, preferably from 15 to 18%

Na₂ O+B₂ O₃ +K₂ O between 22 and 33%, especially 25 and 30%.

It preferably includes the following compounds, as weight percentages:

    ______________________________________    SiO.sub.2    52 to 64%,                           preferably 55 to 63%    Na.sub.2 O   13 to 18%,                           preferably 14 to 18%    K.sub.2 O    0 to 2%,  preferably 0 to 1%    B.sub.2 O.sub.3                 10 to 15%,                           preferably 11 to 15%    Al.sub.2 O.sub.3                 0 to 4%,  preferably 0.5 to 2%    CaO          4 to 10%, preferably 4 to 8%    MgO          1 to 6%,  preferably 3 to 5%    P.sub.2 O.sub.5                 0 to 3%,  especially 0 to 2%.    ______________________________________

As in the case of class B, this class of compositions is thereforesomewhat intermediate in terms of coefficient α. The compositions ofthis class preferably act as "compositions of lower α", although it isnot excluded from the invention that they may act as a "composition ofhigher α" in combination with a composition with a still lower value ofα.

The compositions of class C tend to be richer in B₂ O₃ and less rich insodium oxides than those of class B. The sum Na₂ O+B₂ O₃ +K₂ O tendsoverall to be less high, because the increase in proportion of B₂ O₃tends to be generally more important than the decrease in the proportionof Na₂ O (and/or K₂ O).

The fourth class of compositions is so-called of type D. It has athermal expansion coefficient α of between 60 and 75×10⁻⁷ K⁻¹. Itincludes sodium oxide, boron oxide, and optionally potassium oxide inthe following proportions, as weight percentage:

Na₂ O≦13%, a especially between 8 and 13% or between 9 and 12%,

B₂ O₃ ≧13%, especially between 14 and 21% or between 15 and 19%

Na₂ O+B₂ O₃ +K₂ O between 21 and 32%, especially between 25 and 30%.

The inorganic composition "D" preferably includes the followingcompounds, as weight percentages:

    ______________________________________    SiO.sub.2    53 to 62%,                           preferably 55 to 60%    Na.sub.2 O   8 to 15%, preferably 9 to 13%    K.sub.2 O    0 to 3%,  preferably 0 to 1%    B.sub.2 O.sub.3                 13 to 22%,                           preferably 15 to 19%    Al.sub.2 O.sub.3                 0 to 3%,  preferably 0.5 to 2%    CaO          4 to 10%, preferably 4 to 7%    MgO          1 to 9%,  preferably 3 to 8%    P.sub.2 O.sub.5                 0 to 3%.    ______________________________________

This class of compositions is therefore aimed at very low coefficientsα, which are to a large extent linked with a high proportion of boronoxide and a relatively moderate proportion of sodium oxide. It istherefore employed in the invention as a composition "of lower α". Thesum (Na₂ O+B₂ O₃ +K₂ O) of this class of compositions does not differappreciably from that of class C or of class A in particular.

This class of compositions can be divided up into various subgroups.Some of these compositions may thus contain P₂ O₅ and others not.Similarly, some of these compositions may contain little or no alumina(0 to 0.5% by weight) or a more significant content, for example of theorder of 1 to 2 or 3%. Similarly, in this class there is a tendency toprefer employing a fairly constant CaO content of the order of 3 to 8%.On the other hand, it may be found advantageous to modify more widelythe proportion of MgO, which may, for example be either also of theorder of 3 to 5%, so as to have an MgO/CaO ratio of the order of 1, orbe of the order of 7 to 9%, so as to have an MgO/CaO ratio rather of theorder of 2, and so additionally to have a higher overall content ofalkaline-earth metal oxides, generally accompanied by a lower SiO₂content.

The fibres according to the invention therefore combine two compositionsbelonging to two different "types". Four combinations are found to bevery particularly advantageous.

The first consists in combining a composition of type "A" as acomposition "of higher α" with a composition of type "C" as acomposition "of lower α", preferably with:

(i) Δ B₂ O₃ ≧3%, especially>7%, preferably between 8 and 15%,

(ii) Δ Na₂ O≧4%, especially≧5%, preferably between 5 and 11%.

The second consists in combining a composition of type "B" as acomposition "of higher α" with a composition of type "D" as acomposition "of lower α", preferably with:

(i) Δ B₂ O₃ ≧3%, especially≧7%, preferably between 8 and 14%,

(ii) Δ Na₂ O≧2%, especially≧6%, preferably between 7 and 10%.

The third consists in combining a composition of type "A" as acomposition "of higher α" with a composition of type "D" as acomposition "of lower α", preferably with:

(i) Δ B₂ O₃ ≧5%, especially≧9%, preferably between 10 and 19%,

(ii) ΔNa₂ O≧5%, especially≧8%, preferably between 8 and 15%.

The fourth consists in combining a composition of type C as acomposition "of higher α" with a composition of type D as a composition"of lower α", preferably with:

(i) Δ B₂ O₃ ≧3%, especially≧6%, preferably between 6 and 9%,

(ii) Δ Na₂ O≧3%, especially≧6%, preferably between 6 and 10%.

It is also possible to envisage combining a composition of type A as acomposition "of higher α" with a composition of type B as a composition"of lower α", preferably with:

(i) Δ B₂ O₃ ≧2%, preferably≧3% up to 8%,

(ii) Δ Na₂ O≧4%, preferably≧5%, especially between 6 and 8%.

The fibres of the invention, as described above, can be applied to themanufacture of materials for thermal and/or sound insulation and also tothe manufacture of substrates for soilless cultivation.

The invention will be described in greater detail below with the aid ofexamples of embodiment, no limitation being implied thereby.

All the mineral wools described below are obtained by internalcentrifuging, the technique of which has been adapted to permit thejoint formation of fibres of two compositions.

In accordance with this "conjoint" internal centrifuging technique,described especially in U.S. Pat. No. 2,998,620, a fibre-forming spinneris fed continuously with a thread of molten glass exhibiting a givenfirst composition and with a thread of molten glass exhibiting a secondcomposition. These compositions are chosen according to the invention soas to exhibit significantly different coefficients α. Under the effectof the centrifugal force and of the suitable design of the orifices withwhich the spinner is provided, two-component filaments are ejected fromthe orifices and then drawn with the aid of an annular burner generatinga crown ring of hot gas under the spinner. The fibres thus formed arenext optionally impregnated with a sizing composition, with annularblowing members next guiding the optionally sized fibres onto a suctionconveyor belt the speed of which will make it possible to adjust theweight per unit area of the final product. The sheet thus formed istaken into an oven at 200° C. equipped with lower and upper endlessforming belts (which allows the resin of the sizing composition tocrosslink, if one has been employed), and to form the sheet of thedesired thickness and hence of the desired density.

The four tables below group together examples of compositions accordingto the four large classes of compositions A to D detailed above:

Table 1: Compositions of type A, Examples 1A to 18A,

Table 2: Compositions of type B, Examples 1B to 8B,

Table 3: Compositions of type C, Examples 1C to 12C,

Table 4: Compositions of type D, Examples 1D to 13D.

Each of these tables shows: the compositions of the examples and theirT_(log3) and T_(liq) temperatures in ° C. and their thermal expansioncoefficients α in K⁻¹.

Fe₂ O₃ should be understood as taking into account all of the ironoxides in the composition, in a way which is accepted in this field.

In all these examples the contents are to be understood as weightpercentages. When the sum of all the contents of all the compounds isslightly lower than 100%, it should be understood that the residualproportion corresponds to the impurities and/or minor components whichare not analysed (for example traces of Fe₂ O³, of TiO₂, of SO₃, etc.).If, on the other hand, it is slightly more than 100%, the reason is thepermitted tolerances of the analyses in this field.

                                      TABLE 1    __________________________________________________________________________    COMPOSITION "A"        EX. 1A EX. 2A                     EX. 3A EX. 4A                                  EX. 5A EX. 6A                                               EX. 7A EX. 8A                                                            EX.    __________________________________________________________________________                                                            9A    SiO.sub.2        56.52  53.48 54.64  51.5  56     54.5  56     50.5  53.5    Al.sub.2 O.sub.3        4.7    4.6   4.65   7     6.5    7     4.5    7     7    CaO 7      7     7      9     9      8     9      9     9    MgO 2.1    2.05  2.1    2.5   2.5    2.5   2.5    2.5   2.5    Na.sub.2 O        21.9   22    21.9   25    19     23    23     25    23    K.sub.2 O        1.1    1.1   1.1    2     2      2     2      2     2    B.sub.2 O.sub.3        5.8    5.8   5.9    3     5      3     3      4     3    Fe.sub.2 O.sub.3        --     1.4   0.16   --    --     --    --     --    --    F   0.75   0.75  0.7    --    --     --    --     --    --    NiO 0.01   1     1      --    --     --    --     --    --    CoO --     0.85  0.85   --    --     --    --     --    --    P.sub.2 O.sub.5        0.05   0.03  0.03   0     0      0     0      0     0    TOTAL        99.93  100.06                     100.03 100   100    100   100    100   100    T.sub.log3        937    896   907    902   978    948   937    889   937    T.sub.liq        860    860   870    --    --     --    --     --    --    α        117 × 10.sup.-7               117 × 10.sup.-7                     116 × 10.sup.-7                            131 × 10.sup.-7                                  110 × 10.sup.-7                                         123 × 10.sup.-7                                               123 × 10.sup.-7                                                      131 × 10.sup.-7                                                            124 ×                                                            10.sup.-7    __________________________________________________________________________    COMPOSITION "A"        EX. 10A               EX. 11A                     EX. 12A                            EX. 13A                                  EX. 14A                                         EX. 15A                                               EX. 16A                                                      EX. 17A                                                            EX.    __________________________________________________________________________                                                            18A    SiO.sub.2        53     50    51     51    51     54.5  55     58.5  60    Al.sub.2 O.sub.3        8      7     8      7     8      1.5   0.5    2.5   2.5    CaO 12     12    12     12    10     12    12     12    12    MgO 2      2     2      2     2      2     2.5    2     2.5    Na.sub.2 O        22     25    25     25    25     25    25     22    22    K.sub.2 O        3      2     2      3     3      3     3      0     0    B.sub.2 O.sub.3        0      0     0      0     0      0     0      1     1    Fe.sub.2 O.sub.3        --     --    --     --    --     --    --     --    --    F   --     --    --     --    --     --    --     --    --    NiO --     --    --     --    --     --    --     --    --    CoO --     --    --     --    --     --    --     --    --    P.sub.2 O.sub.5        0      2     0      0     1      2     2      2     0    TOTAL        100    100   100    100   100    100   100    100   100    T.sub.log3        951    913   913    900   923    900   895    948   943    T.sub.liq        --     --    --     --    --     --    --     --    --    α        128 × 10.sup.-7               138 × 10.sup.-7                     137 × 10.sup.-7                            138 × 10.sup.-7                                  137 × 10.sup.-7                                         135 × 10.sup.-7                                               134 × 10.sup.-7                                                      122 × 10.sup.-7                                                            120 ×                                                            10.sup.-7    __________________________________________________________________________

                                      TABLE 2    __________________________________________________________________________    COMPOSITION "B"    EX. 1B    EX. 2B                    EX. 3B                          EX. 4B                                EX. 5B                                      EX. 6B                                            EX. 7B                                                  EX. 8B    __________________________________________________________________________    SiO.sub.2        58    60    59.5  59.5  59    58    61    61.8    Al.sub.2 O.sub.3        2.5   2     2.5   1     2.5   2.5   7     2.5    CaO 9     9     9     9     9     9     9     6.9    MgO 4     3.5   4     4     4     4     2.5   2.5    Na.sub.2 O        19    19    19    17.5  18    18    17.5  19.6    K.sub.2 O        2     2     2     2     2     2     2     1.9    B.sub.2 O.sub.3        5.5   4.5   4     7     5.5   6.5   7     4.6    TOTAL        100   100   100   100   100   100   100   99.80    T.sub.log3        910   925   925   915   930   910   925   1003    T.sub.liq        --    --    --    --    --    --    --    890    α        107 × 10.sup.-7              107 × 10.sup.-7                    107 × 10.sup.-7                          100 × 10.sup.-7                                104 × 10.sup.-7                                      103 × 10.sup.-7                                            100 × 10.sup.-7                                                  110 × 10.sup.-7    __________________________________________________________________________

                                      TABLE 3    __________________________________________________________________________    COMPOSITION "C"        EX. 1C              EX. 2C                    EX. 3C                          EX. 4C                                EX. 5C                                      EX. 6C    __________________________________________________________________________    SiO.sub.2        58    58.5  61    57.81 59    62.15    Al.sub.2 O.sub.3        1     0.5   0.5   0.65  0.5   0.04    CaO 7     7     7     7.95  7     10.7    MgO 5     5     3.5   3.4   4.5   0.9    Na.sub.2 O        14    14    14    17.9  14    13.75    K.sub.2 O        0     0     0     0.02  0     0.02    B.sub.2 O.sub.3        15    15    14    11.9  15    12.15    BaO 0     0     0     0     0     0    P.sub.2 O.sub.5        0     0     0     0     0     0    TOTAL        100   100   100   99.63 100   99.71    T.sub.log3        956   956   983   929   960   989    T.sub.liq        --    --    --    870   --    940    α        80 × 10.sup.-7              80 × 10.sup.-7                    80 × 10.sup.-7                          98 × 10.sup.-7                                78 × 10.sup.-7                                      85 × 10.sup.-7    __________________________________________________________________________    COMPOSITION "C"        EX. 7C              EX. 8C                    EX. 9C                          EX. 10C                                EX. 11C                                      EX. 12C    __________________________________________________________________________    SiO.sub.2        58    60.5  52    55.2  53    55    Al.sub.2 O.sub.3        1     1.5   2     1.35  1     1    CaO 7     7     8     7.6   10    9    MgO 4     3.5   7     3.1   7     7    Na.sub.2 O        15    15.5  15    17.85 15    15    K.sub.2 O        0     0     2     0.s   1     2    B.sub.2 O.sub.3        15    12    12    12.2  12    11    BaO 0     0     0     2.35  0     0    P.sub.2 O.sub.5        0     0     2     0     1     0    TOTAL        100   100   100   100.15                                100   100    T.sub.log3        947   984   924   920   914   926    T.sub.liq        --    --    --    850   --    --    α        83 × 10.sup.-7              87 × 10.sup.-7                    90 × 10.sup.-7                          99 × 10.sup.-7                                90 × 10.sup.-7                                      90 × 10.sup.-7    __________________________________________________________________________

                                      TABLE 4    __________________________________________________________________________    COMPOSITION "D"        EX. 1D              EX. 2D                    EX. 3D                          EX. 4D                                EX. 5D                                      EX. 6D                                            EX. 7D    __________________________________________________________________________    SiO.sub.2        56.32 57.5  59    59    58.5  57    59    Al.sub.2 O.sub.3        2.7   1     0.5   1     1     2.5   1    CaO 8.4   8     8.5   9     9     9     9    MgO 3.4   4     5     3.5   4     4     3.5    Na.sub.2 O        9.7   11.5  12    10.5  10.5  11.5  11    K.sub.2 O        0.02  0     0     0     0     0     0    B.sub.2 O.sub.3        19.29 18    15    17    17    16    16.5    P.sub.2 O.sub.5        0     0     0     0     0     0     0    TOTAL        99.83 100   100   100   100   100   100    T.sub.log3        1004  955   973   979   975   971   977    T.sub.liq        970   --    --    --    --    --    --    α        70 × 10.sup.-7              72 × 10.sup.-7                    75 × 10.sup.-7                          70 × 10.sup.-7                                70 × 10.sup.-7                                      75 × 10.sup.-7                                            72 × 10.sup.-7    __________________________________________________________________________    COMPOSITION "D"        EX. 8D EX. 9D EX. 10D                             EX. 11D                                    EX. 12D                                           EX. 13D    __________________________________________________________________________    SiO.sub.2        59     59     57     55.5   53.5   55    Al.sub.2 O.sub.3        1      1      2.5    0.5    0.5    1    CaO 8      9      9      8      9      8    MgO 4      4      4      8      8      7    Na.sub.2 O        11     11.5   11.5   9      9      10    K.sub.2 O        0      0      0      0      0      0    B.sub.2 O.sub.3        17     15.5   16     19     19     19    P.sub.2 O.sub.5        0      0      0      0      1      0    TOTAL        100    100    100    100    100    100    T.sub.log3        977    978    971    949    938    941    T.sub.liq        --     --     --     --     --     --    α        70 × 10.sup.-7               74 × 10.sup.-7                      75 × 10.sup.-7                             62 × 10.sup.-7                                    64 × 10.sup.-7                                           66 × 10.sup.-7    __________________________________________________________________________

The compositions of a given type are next combined with compositions ofanother type so as to conform to the conditions of the invention interms of Na₂ O and of B₂ O₃ contents and of coefficient α. The mostadvantageous combinations are those which combine compositions of type Awith compositions of type C (combination "A+C") , Compositions of type Bwith compositions of type D (combinations "B+D"), and compositions oftype A with compositions of type D ("combinations "A+D"). These are, infact, the combinations which make it possible to ensure the mostsignificant differences in coefficient α, combined with the smallestdifferences in T_(log3) It is thus possible to obtain wavy fibreswithout being "at the limit" both in terms of difference in thermalexpansion and in compatibility of fibre-forming.

Nevertheless, by carefully choosing the compositions, it is possible tocombine compositions of type A and B or compositions of type C and D.

It is found that it is also possible to form combinations withcompositions belonging to different classes but nevertheless havingT_(log3) values which are sufficiently close.

Thus:

from Table 1 it is seen that the compositions according to class A canexhibit T_(log3) values ranging between 800° and 990° C.,

from Table 2 it is seen that the compositions according to class B canexhibit T_(log3) values ranging between 890° C. and 950° C., with evenone example at approximately 1000° C.,

from Table 3 it is seen that the compositions according to class C canexhibit T_(log3) values ranging between 900 and 990° C.,

and, finally, from Table 4 it is seen that the compositions according toclass D can exhibit T_(log3) values which are generally between 920° C.and 980° C., with even a value of approximately 1000° C. in the case ofExample 1 D. (These ranges of T_(log3) are given merely by way ofindication and without limiting any of the classes).

Table 5 below proposes the most advantageous combinations, by indicatingfor each one the values of Δ Na₂ O, Δ B₂ O₃, |Δ Na₂ O-Δ B₂ O₃ | asweight percentages explained in detail at the beginning of the presenttext, as well as the values of Δα in K⁻¹ corresponding to the differencebetween the coefficients α of the composition "of higher α" and of thecomposition "of lower α" and the values of Δ T_(log3) in degrees C,corresponding to the difference, in absolute values, between theT_(log3) temperature of the composition "of higher α" and that of thecomposition "of lower α".

                  TABLE 5    ______________________________________                                          |ΔNa.sub.2 O-             Δα                    Δ T.sub.log3                            ΔNa.sub.2 O                                    ΔB.sub.2 O.sub.3                                          ΔB.sub.2 O.sub.3|    ______________________________________    "Combination A + C"    EX. 1A + EX. 1C               37 × 10.sup.-7                        19      7.9   9.2   1.3    EX. 4A + EX. 4C               33 × 10.sup.-7                        27      7.1   8.9   1.8    EX. 5A + EX. 5C               32 × 10.sup.-7                        18      5     10    5    EX. 7A + EX. 7C               40 × 10.sup.-7                        10      8     12    4    EX. 10A + EX. 7C               45 × 10.sup.-7                        4       7     15    8    EX. 12A + EX. 4C               39 × 10.sup.-7                        16      10    15    5    EX. 14A + EX. 4C               39 × 10.sup.-7                        6       7.1   11.9  4.8    EX. 12A + EX. 9C               47 × 10.sup.-7                        11      10    12    2    "Combination B + D"    Ex. 2B + EX. 2D               35 × 10.sup.-7                        30      7.5   13.5  6    EX. 8B + EX. 1D               40 × 10.sup.-7                        1       9.9   14.69 4.79    EX. 5B + EX. 12D               40 × 10.sup.-7                        8       9     13.5  4.5    "Combination A + D"    EX. 6A + EX. 13D               57 × 10.sup.-7                        7       13    16    3    EX. 1A + EX. 12D               53 × 10.sup.-7                        1       12.9  13.2  0.3    EX. 10A + EX. 2D               56 × 10.sup.-7                        1       10.5  18    7.5    EX. 18A + EX. 11D               58 × 10.sup.-7                        6       13    18    5    EX. 5A + EX. 9D               36 × 10.sup.-7                        0       7.5   10.5  3    "Combination C + D"    Ex. 4C + EX. 11D               36 × 10.sup.-7                        20      8.9   7.1   1.8    EX. 10C + EX. 12D               35 × 10.sup.-7                        18      8.85  6.8   2.05    "Combination A + B"    EX. 8A + EX. 6B               28 × 10.sup.-7                        21      7     2.5   4.5    EX. 13A + EX. 4B               38 × 10.sup.-7                        15      7.5   7     0.5    ______________________________________

Of course, this table absolutely does not delimit all the possiblecombinations. It exemplifies compositions that make it possible toobtain wavy fibres without encountering particular difficulties duringthe fibre formation and without the raw materials needed for thecompositions excessively overloading their overall production cost. Itmay also be noted that even the compositions of low coefficient α, whichare those richest in B₂ O₃, have B₂ O₃ contents which remain, by weight,lower than 20%; and that even the compositions of highest coefficient α,which are those richest in Na₂ O, have Na₂ O contents which remain atmost 25%.

The invention has therefore made it possible to reconcile thepreparation of mineral wool with very specific properties withconditions of manufacture which are acceptable industrially andeconomically.

We claim:
 1. Two-component inorganic fibres conjointly formed from firstand second inorganic compositions, each composition:a) comprisingsilica, alkali metal oxides and alkaline earth metal oxides, and havingless than a combined total of at most 1% by weight of titanium oxide,zinc oxide, barium oxide and lithium oxide; b) has a minimum viscositytemperature, (T_(log) 3), of from 830 to 1010° C.; c) has a differencebetween its minimum viscosity temperature and its liquidus temperatureof at least 30° C.; wherein the compositions are different and: d) thecompositions have thermal expansion coefficients differing by at least20×10⁻⁷ °K⁻¹ ; e) the compositions comprise contents of boron oxide andsodium oxide in which the amount by weight of each of these componentsin the first composition differs from the corresponding amounts in thesecond composition by more than 2%; f) one of the compositions comprisesup to 8% by weight of potassium oxide; g) one of the compositions iscomposition "C" which has a thermal expansion coefficient of from76×10⁻⁷ °k⁻¹ to 99×10⁻⁷ °K⁻¹ and further comprises sodium oxide, boronoxide and optionally potassium oxide such that the proportions by weightof these components are as follows: from 9 to less than 15% by weight ofboron oxide, 13 to 18% by weight of sodium oxide and the combinedproportions of the three components is from 22 to 33% by weight; and h)the other composition is composition "A" which comprises sodium oxideand optionally boron oxide and potassium oxide, wherein boron oxide ispresent in an amount of from 0 to 7% weight percent.
 2. Two-componentinorganic fibres according to claim 1 in which the first and secondcompositions have differing sodium oxide contents, (ΔNa₂ O), and boronoxide contents, (ΔB₂ O₃), that obey the relationship ΔNa₂ O-ΔB₂ O₃ is atleast zero but not more than
 5. 3. Two-component inorganic fibresaccording to claim 1 in which at least one of the two components furthercomprises at least 0.5% by weight of alumina.
 4. Two-component inorganicfibres according to claim 3 in which at least one of the two componentsfurther comprises at most 5% by weight of alumina.
 5. Two-componentinorganic fibres according to claim 1 in which at least one of the twocomponents further comprises from 0 to 3% by weight of phosphoruspentoxide.
 6. Two-component inorganic fibres according to claim 1 inwhich at least one of the two components further comprises from 0 to 3%,by weight of ferric oxide, expressed as total iron.
 7. Two-componentinorganic fibres according to claim 1 which Component "C" comprisessilica, calcia and magnesia and optionally alumina and phosphoruspentoxide in the following proportions by weight:

    ______________________________________    SiO.sub.2   52-64%    Na.sub.2 O  13-18%    K.sub.2 O   0-2%    B.sub.2 O.sub.3                10-less than 15%    Al.sub.2 O.sub.3                0-4%    CaO          4-10%    MgO         1-6%    P.sub.2 O.sub.5                 0-3%.    ______________________________________


8. Two-component inorganic fibres according to claim 7 in whichComponent "C" comprises the following components in the proportions byweight indicated:

    ______________________________________    SiO.sub.2   55-63%    Na.sub.2 O  14-18%    K.sub.2 O   0-1%    B.sub.2 O.sub.3                11-less than 15%    Al.sub.2 O.sub.3                0.5-2.5%    CaO         4-8%    MgO         3-5%    P.sub.2 O.sub.5                 0-3%.    ______________________________________


9. Two-component inorganic fibres according to claim 7 in whichcomposition "A" has a thermal expansion coefficient of from 110×10⁻⁷°K⁻¹ to 140×10⁻⁷ °K⁻¹ and wherein sodium oxide is present in an amountof from 18-25% and the combined proportions of sodium oxide, boron oxideand potassium oxide and is from 18-33%.
 10. Two-component inorganicfibres according to claim 9 in which Component "A" comprises silica,calcia and magnesia and optionally alumina, and phosphorus pentoxide inthe following proportions by weight:

    ______________________________________            SiO.sub.2                  46-62%            Na.sub.2 O                  18-25%            K.sub.2 O                  0-8%            B.sub.2 O.sub.3                  0-7%            Al.sub.2 O.sub.3                   0-12%            CaO    6-13%            MgO   0-5%            P.sub.2 O.sub.5                   0-3%.    ______________________________________


11. Two-component inorganic fibres according to claim 10 in whichComponent "C" comprises the following components in the proportions byweight indicated:

    ______________________________________           SiO.sub.2                 48-60%           Na.sub.2 O                 19-25%           K.sub.2 O                 1-4%           B.sub.2 O.sub.3                 0-4%           Al.sub.2 O.sub.3                 0.5-5%           CaO    7-12%           MgO   0-3%           P.sub.2 O.sub.5                  0-3%.    ______________________________________